title: Cyclopeptide alkaloids: stereochemistry and synthesis of the precursors of discarines C and D and myrianthine A.
abstract: The stereochemistry of discarines C (1) and D (2) and myrianthine A (3), three cyclopeptide alkaloids isolated from Discaria febrifuga, was determined by a combination of NMR studies of 1-3, enantioselective gas chromatography, and comparison of NMR data with those of synthetic tripeptides. For the synthesis of peptides, the nonproteinogenic amino acid 3-phenylserine was also obtained in its four diastereoisomeric forms (l and d threo, obtained by recrystallization of the diastereoisomeric tripeptide, and l and d erythro, obtained by a Mitsunobu reaction with the threo-tripeptides). The general synthetic strategy described in this paper allows the tripeptide to be obtained with the free N-terminal extremity protected or dimethylated. This strategy also allows the synthesis of the corresponding peptide with an imidazolidinone ring.
authors.affiliation: Departamento de Química, Universidade Federal de Sergipe, CEP 49100-000. Rod. Marechal Randon, s/n Jardin Rosa Elze, São Cristóvão, SE, Brazil.
authors.forename: Marco A
authors.initials: MA
authors.lastname: Mostardeiro
authors.forename: Vinicius
authors.initials: V
authors.lastname: Ilha
authors.forename: Janice
authors.initials: J
authors.lastname: Dahmer
authors.forename: Miguel S B
authors.initials: MS
authors.lastname: Caro
authors.forename: Ionara I
authors.initials: II
authors.lastname: Dalcol
authors.forename: Ubiratan F
authors.initials: UF
authors.lastname: da Silva
authors.forename: Ademir F
authors.initials: AF
authors.lastname: Morel
mesh_terms: D000470:Alkaloids / Q000737:chemistry / Q000302:isolation & purification*; D001938:Brazil; D002849:Chromatography, Gas; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010456:Peptides, Cyclic / Q000138:chemical synthesis / Q000737:chemistry / Q000302:isolation & purification*; D024301:Plant Bark / Q000737:chemistry; D018517:Plant Roots / Q000737:chemistry; D027823:Rhamnaceae / Q000737:chemistry*; D012694:Serine / Q000031:analogs & derivatives; D013237:Stereoisomerism
chemical_list: D000470:Alkaloids; D010456:Peptides, Cyclic; C584222:discarine C; C584223:discarine D; C584224:myrianthine A; D012694:Serine; C467259:phenylserine